Critically endangered Black rhino (Diceros bicornis): Habitat loss and illegal harvest have reduced once abundant populations to a worldwide total of under 2,500. Only sustained conservation effort will allow the continued survival of the species. (Credit: iStockphoto/Alan Crawford)

That's according to a new study by University of Adelaide and Macquarie University scientists which has shown that populations of endangered species are unlikely to persist in the face of global climate change and habitat loss unless they number around 5000 mature individuals or more.

The findings have been published online in the journal Biological Conservation.

"Conservation biologists routinely underestimate or ignore the number of animals or plants required to prevent extinction," says lead author Dr Lochran Traill, from the University of Adelaide's Environment Institute.

"Often, they aim to maintain tens or hundreds of individuals, when thousands are actually needed. Our review found that populations smaller than about 5000 had unacceptably high extinction rates. This suggests that many targets for conservation recovery are simply too small to do much good in the long run."